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91.
Rodrigues AC Nascimento ML Bragatto CB Souquet JL 《The Journal of chemical physics》2011,135(23):234504
Conductivity data of the xAgI(1 - x)AgPO(3) system (0 ≤ x ≤ 0.5) were collected in the liquid and glassy states. The difference in the dependence of ionic conductivity on temperature below and above their glass transition temperatures (T(g)) is interpreted by a discontinuity in the charge carrier's mobility mechanisms. Charge carrier displacement occurs through an activated mechanism below T(g) and through a Vogel-Fulcher-Tammann-Hesse mechanism above this temperature. Fitting conductivity data with the proposed model allows one to determine separately the enthalpies of charge carrier formation and migration. For the five investigated compositions, the enthalpy of charge carrier formation is found to decrease, with x, from 0.86 to 0.2 eV, while the migration enthalpy remains constant at ≈0.14 eV. Based on these values, the charge carrier mobility and concentration in the glassy state can then be calculated. Mobility values at room temperature (≈10(-4) cm(2) V(-1) s(-1)) do not vary significantly with the AgI content and are in good agreement with those previously measured by the Hall-effect technique. The observed increase in ionic conductivity with x would thus only be due to an increase in the effective charge carrier concentration. Considering AgI as a weak electrolyte, the change in the effective charge carrier concentration is justified and is correlated to the partial free energy of silver iodide forming a regular solution with AgPO(3). 相似文献
92.
We investigate the problem of heat conduction across molecular junctions connecting two nanoparticles, both in vacuum and in a liquid environment, using classical molecular dynamics simulations. In vacuum, the well-known result of a length independent conductance is recovered; its precise value, however, is found to depend sensitively on the overlap between the vibrational spectrum of the junction and the density of states of the nanoparticles that act as thermal contacts. In a liquid environment, the conductance is constant up to a crossover length, above which a standard Fourier regime is recovered. 相似文献
93.
Jean-Louis Féménias 《Journal of Molecular Spectroscopy》2005,232(1):80-101
Applications of the χ2 test, the F test, the Durbin-Watson d test, and the f (or Sign) test, to examples of correlated data treatment, show important drawbacks with the d test and (apparently) with the f test. An analytical approach based on residual analysis suggests an improvement in their use that leads to better results at lowest order; it also points out a distinction between goodness-of-fit tests, as the f test, and goodness-of-modeling tests, as the χ2 and F tests. The residual analysis method is applied to the same examples; it looks faster, simpler, and often more accurate than the classical ones. 相似文献
94.
S. Colis M. Guth J. Arabski A. Dinia D. Muller 《Journal of magnetism and magnetic materials》2002,240(1-3):186-188
Hard-soft spin valve structures have been grown by molecular beam epitaxy on MgO(0 0 1) substrates. The hard magnetic layer consists of an artificial Co/Ir/Co ferrimagnet system (AFi), while a Fe/Co bilayer from the buffer has been used as a soft detection layer. The Fe layer has been grown at 600°C giving rise to a monocrystalline layer with a BCC structure. Consequently, this layer presents a hard and a easy magnetization axis, respectively, along the BCC [1 1 0] and the [1 0 0] directions. The AFi system presents dramatic differences after successive annealing steps up to 350°C. An increase of the GMR from 3% to 3.5% is observed after annealing at 250°C while the coercive field of the AFi and the GMR plateau are strongly reduced. After further annealing at higher temperature the GMR drops down accompanied with a strong decrease in the antiparallel alignment amount in the AFi system. Rutherford back scattering measurements have been performed to investigate the changes in the interface morphology and to correlate it to the magneto-transport properties. 相似文献
95.
While the striking structures (e.g. nest architecture, trail networks) of insect societies may seem familiar to many of us, the understanding of pattern formation still constitutes a challenging problem. Over the last two decades, self-organization has dramatically changed our view on how collective decision-making and structures may emerge out of a population of ant workers having each their own individuality as well as a limited access to information. A variety of collective behaviour spontaneously outcome from multiple interactions between nestmates, even when there is no directing influence imposed by an external template, a pacemaker or a leader. By focussing this review on foraging structures, we show that ant societies display some properties which are usually considered in physico-chemical systems, as typical signatures of self-organization. We detail the key role played by feed-back loops, fluctuations, number of interacting units and sensitivity to environmental factors in the emergence of a structured collective behaviour. Nonetheless, going beyond simple analogies with non-living self-organized patterns, we stress on the specificities of social structures made of complex living units of which the biological features have been selected throughout the evolution depending on their adaptive value. In particular, we consider the ability of each ant individual to process information about environmental and social parameters, to accordingly tune its interactions with nestmates and ultimately to determine the final pattern emerging at the collective level. We emphasize on the parsimony and simplicity of behavioural rules at the individual level which allow an efficient processing of information, energy and matter within the whole colony. 相似文献
96.
The field of the rapid characterization of products by HS-MS is reviewed. The general principle of HS-MS systems consists of introducing volatile components present in the HS of a sample without prior chromatographic separation into the ionization chamber of a mass spectrometer. The spectrum resulting from simultaneous ionization and fragmentation of the mixture of molecules introduced constitutes a “fingerprint” that is characteristic of the product being analyzed. Exploitation of this spectral information allows one determine the composition of the sample. 相似文献
97.
The oxide ion conducting systems Bi2O3-Y2O3-Pr6O11 and Bi2O3-Y2O3-ZrO2 have been prepared and studied in order to combine the advantages of stabilized Bi2O3 and ZrO2 solid electrolytes. Coprecipitation of high purity oxides was used for preparation. The formation of the fluorite-type cubic
structure was confirmed by X-ray powder diffraction analysis. The relative contributions of ions and electrons to the total
conductivity were measured by the concentration cell method.
Using Ultraviolet Photoemission Spectroscopy (UPS) we have determined the work function Φ of electrons, the position of the
Fermi level in relation to the valence band edge (EF-EV) and the change of the ionization potential (I) as a function of temperature. For bismuth oxide-based solid electrolytes,
we used an Fe/FeO mixture as reference contact to establish a defined oxygen partial pressure in the solid electrolyte sample.
Oxygen isotope exchange experiments were performed in an exchange cell with a gas regulating system and mass spectrometer
to determine the oxygen surface exchange rate.
Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995 相似文献
98.
A new convenient preparation of samarium dibromide in THF is reported. Pinacol coupling reactions using SmBr2 in catalytic amounts together with mischmetall as a coreductant have been performed with a variety of carbonyl compounds. 相似文献
99.
100.
Tungsten and molybdenum oxide bronzes of the general formulas AxMO3 and AxM6O17 (A=K, Li, Na; M=W, Mo) are well known as electrode materials with good response to pH changes. However, there is also a high
cross sensitivity to other ions, e.g. Na+ or Li+. Currently, the synthesis of tailored materials for special applications is the priority task. Preparation routes such as
fused salt electrolysis, solid state reactions in vacuum or hydrothermal synthesis were studied. New compounds of the general
formula LixMo1−yWyO3 and also AxWO3 (A = bi- or trivalent) have a high technological potential. Preliminary experiments have shown that some of these new materials
possess properties of reference electrodes within a restricted pH range. To prepare electrodes, usually single crystals are
required. This is adverse because of high operating expense of single crystal synthesis. In some cases it is also possible
to use polycrystalline materials for the preparation.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献